Coating composition of an epoxy resin,an aromatic sulfonamide,a silicone resin and a cross-linking catalyst

ABSTRACT

THE NOVEL COATING COMPOSITION IS A MIXTURE OF A LOW MOLECULAR WEIGHT EPOXY RESIN, AN AROMATIC SULFONAMIDE, E.G., NCYCLOHEXYLTOLUENE SULFONAMIDE, A REACTIVE SILICONE RESIN AND A CROSS-LINKING CATALYST, E.G., ZINC OCTOATE. THE COATING COMPOSITION HAS EXCELLENT RELEASE PROPERTIES, STAIN RESISTANCE, WATER REPELLENCY, AND IS USEFUL AS A RELEASE COATING FOR ICECUBE TRAYS, FOR BAKEWARE AND COOKWARE, AND CAN BE UTILIZED TO COAT SINKS, OVEN PARTS AND AS A CLEAR COATING FOR HARDWARE. RIS SELECTED FROM THE GROUP EONSSSRDSEDDDAND S13 .0 DE2 - . AND RQHU 15SRDSE;DDZDR5TED4GROUP CONSISTING

United States Patent Vasta Aug. 29, 1972 [54] COATING COMPOSITION OF AN 2,819,245 1/ 1958 Shorr ..260l824 EPOXY RESIN, AN AROMATIC 3,055,858 9/1962 Frye et a1 ..260/824 SULFONAMIDE A SILICONE RESIN 3,154,597 10/1964 McWhorter ..260/824 AND A CROSS.LINKING Y T 3,533,980 10/1970 Minuto ..260/30.8 [72] Inventor: Joseph A. Vasta, Woodbury, NJ. FOREIGN PATENTS OR APPLICATIONS [73] Assignee: E. I. du Pont de Nemours d C 864,697 4/1961 Great Britain ..260/824 pany Wilmington DeL Canada [22] Filed: 1970 Primary ExaminerDona1d E. Czaja [21] Appl. No.: 98,851 Assistant ExaminerEugene C. Rzucidlo Attorneyl-lolmar L. Fricke [52] US. Cl.....260/18 EP, 117/132 BE, 117/132 BS, [57 ABSTRACT 260/37 EP, 260/47 EP, 260/824 EP 51 Int. Cl. ..C08g 45/16 The 3 9 a of a 10w [58] Field of Search 260/18 EP 824 EP 30 8 R molecular weight epoxy resm, an aromatic sulfona- 'Ei,'" 1177132 mide, e.g., N-cyclohexyltoluene sulfonamide, a reactive silicone resin and a cross-linking catalyst, e.g., zinc octoate. The coating composition has excellent [56] References C'ted release properties, stain resistance, water repellency, UNITED STATES PATENTS and is useful as a release coating for icecube trays, for bakeware and cookware, and can be utilized to coat 2,712,001 6/ I955 Greenlee ..260/47 sinks, oven parts and as a clear coating for hardware,

10 Claims, No Drawings COATING COMPOSITION OF AN EPOXY RESIN, AN AROMATIC SULFONAWE, A SILICONE RESIN AND A CROSS-LINKING CATALYST BACKGROUND OF THE INVENTION This invention relates to a coating composition and in particular, to a high quality coating composition which forms a finish that has excellent release properties.

Coating compositions containing epoxy resins, aromatic sulfonamides or reactive silicone resins are known in the art and coatings manufactured from these various resins are useful for many purposes. In particular, Greenlee US. Pat. No. 2,494,295, issued Jan. 10, 1950, is directed to the formation of coating compositions of resinous epoxides and an aldehyde aryl sulfonamide resin; Greenlee, US. Pat. No. 2,712,001, issued June 28, 1955 is directed to coating compositions containing blends of sulfonamides resins and epoxy resin compositions; coatings of silicone modified epoxy resins are also known. None of the aforementioned coating compositions provide acceptable finishes for contact with foods and finishes with the excellent release properties, stain resistance, water repellency and hardness that is required for many uses, such as coating icecube trays and bakeware.

There is a great need in the coating industry for a high quality coating composition that provides a finish that has food grade acceptability and with the unique characteristics of excellent release properties, stain resistance, water repellency, in combination with hardness and durability. These characteristics have not been provided by the conventional coating compositions. The novel coating composition of this. invention has these aforementioned desirable physical properties.

SUMMARY OF THE INVENTION The coating composition of this invention comprises a solution of -60 percent by weight of the film-forming polymer blend and 90-40 percent by weight of an organic solvent, wherein the film-forming polymer blend consists essentially of the following ingredients:

1. 49-985 percent by weight, based on the weight of the polymer blend, of a low molecular weight epoxy resin and an aromatic sulfonamide having a molar ratio of about 1.5:l to about 2.5:1; wherein epoxy resin is either a. an epoxy hydroxy polyether resin of the general wherein n is a positive integer sufficient to provide an epoxide equivalent (*Epoxide Equivalent grams of resin containing one gram equivalent of epoxide.) of 100-1 ,025 and R is either so so an alkylene radical having two to six carbon atoms or a cyclohexylene group; or

b. one of the following cycloaliphatic epoxy resins:

2. 0.5-50 percent by weight, based on the weight of i the polymer blend, of a reactive silicone resin of the formula R4 lito wherein n is a positive inter sufficiently high to provide a molecular weight of 300 to 4,000; and R and R are either -OCI-I phenyl, or OH; and the composition contains about 0.1-5 percent by weight, based on the weight of the polymer blend, of a cross-linking catalyst.

DESCRIPTION OF THE INVENTION The novel coating composition of this invention is a solution that preferably contains about 20-40 percent by weight of a film-forming polymer blend and -60 percent by weight of a solvent for the polymer blend and can contain 0.1-20 percent by weight pigment. The novel coating composition preferably contains 59-80 percent by weight, based on the weight of the polymer blend, of a low molecular weight epoxy resin and an aromatic sulfonamide in a molar ratio of about 2:1, 15-40 percent by weight of a reactive silicone resin and 0.1-5 percent by weight of a cross-linking catalyst of an organo metal compound.

Finishes of the novel composition have particularly excellent physical properties such as good release properties, stain resistance, water repellency, excellent adhesion to primed and unprimed metal substrates, toughness, hardness, crack and mar resistance. The composition is particularly useful as a release coating for icecube trays and bakeware, as a coating for range parts, plumbing fixture such as sinks, and as a clear coating for hardware items, such as saws, chisels, planes, knives and the like. Also, the coating composition can be utilized as a primary finish for refrigerators, stoves, washers, dryers and the like.

The coating composition is prepared by cold mixing the epoxy resin, aromatic sulfonamide, reactive silicone resin, and a cross-linking agent in a conventional solvent. Typical conventional solvents are, for example, toluene, xylene, butyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, butyl alcohol, hexane, cyclohexanone, cellosolve, cellosolve acetate, and other aliphatic, cycloaliphatic, aromatic hydrocarbons, esters, ethers, ketones and alcohols.

The epoxy resins utilized in preparing the novel coating composition of this invention are either epoxy hydroxy polyether resins, or cycloaliphatic epoxy resins. The epoxy resin is utilized with the aromatic sulfonamide in a molar ratio to about 15:1 to about 215:1 and preferably, a 2:1 molar ratio is utilized.

The epoxy hydroxy polyether resins that are utilized in the novel coating composition of this invention are the reaction products of bisphenol and epichlorohydrin and have the following structural formula where R is an alkylene radical having one to four carbon atoms and n is a positive integer sufficiently large to provide an epoxide equivalent of 100 to 1,025.

One preferred epoxy resin is the reaction product of epichlorohydrin and bisphenol A. Bisphenol A has the following formula:

(Ill-Is This particular epoxy resin gives a finish with desirable physical properties such as toughness and durability.

Another very useful epoxy, resin is the reaction product of epichlorihydrin and bisphenol F. Bisphenol F has the following formula:

This particular resin also gives a quality finish.

Another group of useful epoxy resins are the reaction product of hydrogenated bisphenol and epichlorohydrin. Hydrogenated bisphenol A or hydrogenated bisphenol F can be reacted with epichlorohydrin to prepare these resins.

Aliphatic polyglycidyl ethers of glycidyl ethers of a1- kylene glycols having two to six carbon atoms in the alkylene group can also be used in the novel coating composition of this invention. The following are typically useful resins:

diglycidyl ether of ethylene glycol,

diglycidyl ether of neopentyl glycol,

diglycidyl ether of propane diol,

diglycidyl ether of butane diol,

diglycidyl ether of hexane diol ad the like.

Diglycidyl ethers of cycloaliphatic diols can also be used, such as the diglycidyl ether of cyclohexane diol.

The cycloaliphatic epoxy resins that can be utilized in a coating composition of this invention have the general formula where R is an alkylene radical having one to four carbon atoms. One particularly useful resin wherein R is CH is 3,4-epoxycyclohexylmethyl, 3,4-epoxycyclohexane carboxylate. This compound provides coatings of exceptional quality.

Another useful class of cycloaliphatic epoxy resins are the peracid epoxides, such as vinyl cyclohexene dioxide which has the formula The aromatic sulfonamide utilized in the coating composition of this invention is of the general formula R S0 NH R wherein R is a monovalent aromatic radical and R is either hydrogen, a monovalent cycloaliphatic radical or an alkyl group having one to 18 carbon atoms. Typical aromatic sulfonamides are for example:

para toluene sulfonamide,

N-methyl para toluene sulfonamide,

N-ethyl para toluene sulfonamide,

N-propyl para toluene sulfonamide,

N-butyl para toluene sulfonamide,

N-hexyl para toluene sulfonamide,

N-octyl para toluene sulfonamide,

N-nonyl para toluene sulfonamide,

N-dodecyl para toluene sulfonamide,

N-lauryl para toluene sulfonamide,

N-tridecyl para toluene sulfonamide,

N-quadra decyl para toluene sulfonamide,

N-stearyl para toluene sulfonamide,

benzene sulfonamide,

naphthalene sulfonamide,

N-cyclohexyl toluene sulfonamide, and the like.

One particularly preferred aromatic sulfonamide that forms a finish with excellent release properties is N-cyclohexyl toluene sulfonamide.

The reactive silicone resin utilized in the coating composition of this invention has the following formula Li J.

wherein n is a positive integer sufficiently high to provide a molecular weight of 300 to 4,000; and R and R are either OCH OH, or phenyl. One preferred silicone resin is methylphenyl polysiloxane.

The cross-linking agent utilized in the novel coating composition of this invention is preferably an organometal compound, for example, of zinc, tin, lithium or titanium. Typical compounds that can be used are zinc octoate, tin octoate, lithium octoate, zinc naphthenate, tin naphthenate, lithium naphthenate, alkyl tin dilaurate, such as dibutyl tin dilaurate, and titanate esters such as the reaction product two moles of 2,4-pentanedione and one mole of tetraisopropyl titanate.

Pigments are used in the novel coating composition of this invention in the amounts of 0. l-20.0 percent by weight, and preferably, about 0.3-6.0 percent by weight of pigment, is used. Preferably, the pigment is formed into a mill base using conventional techniques and then is blended with the composition. Examples of the great variety of pigments which are used in the novel coating composition of this invention are metallic oxides, preferably titanium dioxide, zinc oxide, and the like, metal hydroxides, meal flakes, metal powders, sulfides, sulfate, carbonates, carbon black, silica, silicates, hydrophobic silicates, such as silicone treated with silicone dioxide, talc, china clay, iron blues, organic reds, maroons and other organic dyes and lakes.

The novel coating compositions of this invention can be applied to a variety of substrates, for example, metal or glass, by any of the usual application methods, such as spraying, electrostatic spraying, dipping, brushing, flow coating, and the like. These coatings are baked at about 80 C. to 500 C. for about minutes to 2 hours. The resulting coating is about 1-5 mils thick and preferably 1-3 mils thick.

The novel coating composition of this invention has excellent adhesion to bare or treated metals or to metals which have been previously primed or painted with alkyd, epoxy or acrylic enamels. Also, the novel composition can be a highly pigmented coating or can be used as a clear coating.

The following Examples illustrate this invention. The parts and percentages are by weight unless otherwise specified.

following structural formula cellent release properties, has excellent adhesion to the substrate, and water and oil form beads on the coating.

The above ingredients are premixed and about 0.25 part by weight of a catalyst is added to the composition and thoroughly blended with the composition. The catalyst is the reaction product of 2 moles of 2,4-pentanedione and one mole of tetraisopropyl titanate.

The composition is then charged into a conventional sandmill and ground to a 0.0 fineness. The composition is reduced to a spray viscosity using xylene and sprayed on an unprimed aluminum panel. The panel is then baked for 15 minutes at 250 C. The resulting coating is mar-resistant and has a fiat finish and has a pencil hardness of 8H.

What is claimed is:

l. A coating composition comprising l060 percent by weight of a polymer blend and 9040 percent by where n is a positive integer) Silicone resin solution solids in toluene of 50.0

(|)OH3 I Si-O- where n is a positive integer sufficiently large to provide the solution viscosity of about l8.3 centipoises at 25 C. and the resin has a specific gravity of 1.027) Zinc octoate (8% zinc) 2.5 Cyclohexanone 50.0 Total: 300.0

The above ingredients are premixed and charged into a conventional sandmill and ground into a fineness of 0.0. The resulting composition is reduced to a spray viscosity using xylene and sprayed onto an unprimed where n is a positive integer sufficient to provide an aluminum panel. The coating is baked for 15 minutes at 250 C. The resulting coating is mar-resistant, has exepoxide equivalent of l00l025 and R is selected from the group consisting of was an alkylene radical having 2-6 carbon atoms and a cyclohexylene radical;

(b) a cycloaliphatic epoxy resin selected from the group consisting of where R of the above resins is an alkylene radical having l-4 carbon atoms; and the aromatic sulfonamide is of the formula R SO2-NHR wherein R is a monovalent aromatic radical and R is selected from the group consisting of hydrogen, a monovalent cycloaliphatic radical and an alkyl group having l-l 8 carbon atoms;

(2) 05-50% by weight, based on the weight of the polymer blend, of a reactive silicone resin of the formula iii 1 wherein n is a positive integer sufficiently high to provide a molecular weight of 300 to 4000; and R and and R is selected from the group consisting of I -C and-CH 4. The coating composition of claim 2 in which R is and R is selected from the group consisting of 5. The coating composition of claim 2 in which the 20 epoxy resin is 6. The coating composition of claim 2 in which the epoxy is 7. The coating composition of claim 2 in which the aromatic sulfone amide is N-cyclohexyl toluene sulfonamide.

8. The coating composition of claim 2 in which the epoxy resinis of the formula where n is a positive integer sufiicient to provide an epoxide equivalent of -1,025; the aromatic sulfonamide is N-cyclohexyl toluene sulfonamide; R of the silicone resin is -OCH and R is phenyl and catalyst is zinc octoate.

9; The coating composition of claim 2 in which the epoxyresin is aromatic sulfonamide is N-cyclohexyl toluene sulfonamide; R of the silicone resin is -OCH and R is phenyl; and the catalyst is a titanate ester of pentanedione and tetraisopropyl titanate.

10. A metal substrate coated with a dried coalesced layer of the composition of claim 1,

mg UNITED STATES PATENT 01mm CERTEHCATE UP @Q'EQTEN Patent No. 3 7, 79 Dated August 95 97 Inventor(s) Joseph A. Vesta It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

i Claim 1, column 6, line 60, delete formula and insert T the follow/118g formula: OH

"' CH 0 CH o R o CH CH on O\' o R 0on 01(- CH Claim 1, column 7, line 50, after "5%" delete "be" and insert by Claim 5, column 7, line 60, after which" delete "R and insert R Signed and sealed this 30th day of January 1973.

(SEAL) Attest.

EDWARD MQFLETCHER, JR. ROBERT GOT'ISCHALK fitesting Officer Commissioner of Patents J 

